Study On Fault Mechanism Of On-board Voltage Transformer Of Emu

Vehicle voltage transformer is an important high voltage electrical equipment which on the high-speed emu.Its function include electric metering,electric energy metering and so on.But in recent years,Shenyang,Beijing,Shanghai and other high-speed train section have happened the on-board malfunction during the operation of voltage transformer,worse to cause catenary feeder circuit breaker tripping,trains and other serious accidents.Therefore,it is of great significance to study the fault mechanism of the on-board voltage transformer for ensuring the safe operation of high-speed railway emu.The fault types of vehicle-mounted voltage transformer mainly include pollution flash-over,foreign body impact,insulation burning and blasting.In the process of operation,the vehicle-mounted voltage transformer will suffer the over-voltage shock caused by the lifting bow,the off-line of the bow net and the over-equal working condition.The research shows that the over-phase over-voltage of the emu has the greatest impact on the vehicle-mounted voltage transformer.Therefore,this thesis mainly studies the influence of the over-voltage on the voltage transformer when the emu is running in the electric split phase,and makes an optimization design on its internal structure.Firstly,the thesis analyzes the reason of over-voltage appears on the voltage transformer when the emu is passing through the electric split phase and points out the reasons of over voltage appearance in different conditions,and the theoretical calculation under various operating conditions which produces the over voltage amplitude related to the switching operation of power phase angle,and the maximum is about three times as big as the normal voltage.Secondly,the thesis analyzes the reason of voltage transformer’s fault and points out that the over-voltage which appears in the electric split phase can easily cause the weakest insulation of the one side coil of the voltage transformer broken.At the meantime,the over current which caused by the over voltage can make a lot of heat accumulate in the insulation of the voltage transformer.This can cause the damage to the local area near the diffusion,and makes the insulation defect badly.With the longtime impacting of the over voltage and over current,the insulation will be destroyed and cause the voltage transformer’s broken.Then,using the CRH380B emu and its on-board voltage transformer as object of study,simulate the variation of the voltage and current on the voltage transformer by the MATLAB software.And the simulation results approve the thesis is right.Finally,according to the study of the voltage transformer fault,the thesis optimizes the internal structure of the voltage transformer on the emu by increasing winding wire diameter and core area which can increase the limit capacity of voltage transformer,improve the overload ability and extended its working life,reduce the times of voltage transformer breaking down.Both calculate and simulation have approved the prioritization scheme is rationality.And no fault accident has happened since the modified voltage transformer operated in April in 2018.It has approved the prioritization scheme is feasible.